Fragmentation channels of non-fullerene cationic carbon clusters

The unimolecular fragmentation channels of highly excited small cationic carbon clusters have been measured with a time-of-flight mass spectrometer after photofragmentation. The dominant channel is loss of the neutral trimer, for all C⁺N = 10-27 clusters except for N = 11, 12 which decay by monomer emission, and C₂₅⁺ which shows competing loss of C₂ and C₃. The results permit to quantify the role of the rotational entropy in the competition between monomer and trimer decays with the help of energies calculated with density functional theory.